In mechatronic systems, detection of component vibrations may be used to improve positioning or early failure detection. It is often not possible or undesirable to attach sensors to the vibrating components. Moreover, control systems are used in production lines to influence operation of devices used in the production lines.
Near-field acoustic holography (NAH) is a sound source identification technique based on measurements with an array of microphones arranged on a plane (hologram plane) close to a surface of an acoustic source. The array data is transformed to obtain information about the sound pressure and the vibration velocity distribution on the source surface. For example, the source of noise generated by a product may be localized using NAH.
Acoustic sensors in an array set-up are used to record acoustic signals. A method of performing near-field acoustic holography based on such recorded acoustic signals is described by R. Scholte in “Fourier based High-resolution Near-field Sound Imaging”, PhD. Thesis, 2008, Eindhoven University of Technology. This method comprises the following steps. Establishing acoustic data representing a set of near-field acoustic holography measurements at a first set of positions. Applying a spatial frequency transform to the acoustic data to obtain data in a spatial frequency domain. Propagating the frequency-transformed acoustic data to obtain propagated frequency-transformed acoustic data, for example in a source plane. Applying a regularization in a wavenumber domain. Performing an inverse spatial frequency transform, to obtain acoustic data describing the acoustic vibrations at the source plane.